Such guide rods, also called selectors, are employed in large numbers in Jacquard looms. The guide rods are arranged side-by-side and stacked on top of each other, as described, for example, in G 9112552.9, EP 0494044 A1 and SK 277761.
Jacquard looms are shed-forming devices for weaving woven fabrics having large patterns. The Jacquard loom raises and lowers each warp end individually, so that woven items with a practically unlimited variety of patterns can be produced.
Conventional Jacquard looms use electronic modules with electromagnets to controllably raise and lower the individual warp threads. Blades are provided to raise and lower so-called lamellae or collar boards disposed on the guide rods. Hooks are suspended from the collar boards. Harness cords are suspended from the free ends of the hooks. These harness cords in turn are coupled to the individual warp ends. When the hook is raised, the warp end which is suspended from the hook, is also raised. A warp end can only be raised, if a collar board is maintained in its upper position. To provide a better understanding of the operation of the Jacquard looms, reference is made to the aforementioned documents.
In conventional Jacquard looms, a large number of guide rods having integrated magnet systems for attracting the Jacquard lamellae are arranged on a computer controlled PC board. Exemplary Jacquard looms may have, for example, 22 of such guide rods arranged side-by-side. The lamellae are also arranged consecutively, so that a Jacquard loom may include several hundred such guide rods.
The maximum packing density is limited by the overall height of the guide rods, since a magnet system is incorporated in each of the guide rods. The magnet system should be large enough to produce a sufficiently strong magnetic force so as to reliably attract the Jacquard lamellae when current flows through the magnet coils.
In conventional guide rods of Jacquard looms, each guide rod includes two adjacent excitation coils, which are connected in series, to attract the lamellae made of sheet metal through a magnetic force (see, for example, SK 277761 and FIGS. 4 and 5 of EP 0494044 A1). Each of the two excitation coils is disposed on an iron core having a circular cross section. A complete magnet system is formed by covering the front faces of the two excitation coils with pole strips made of sheet metal, hereafter referred to as pole strips. The conventional magnet system has to have sufficient height to produce a sufficiently strong magnetic force to attract the Jacquard lamellae, as well as a sufficiently large holding force, when current flows through the excitation coils. An exemplary pair of excitation coils may have, for example, 1420 turns and produce a holding force of 0.42 N at a DC current of approximately of 115 mA. The overall height of the magnet system, i.e., the length of the excitation coils and the iron cores, respectively, in the axial direction of the exemplary pair of excitation coils is approximately 13 mm. This height can therefore limit the maximum attainable packing density of the guide rods.
It is therefore desirable to provide magnets with a smaller overall height for conventional guide rods of a Jacquard loom to increase the packing density.